Optical coherence domain reflectometry (OCDR) is a technique initially developed to provide a higher resolution over optical time domain reflectometry (OTDR) for the characterization of the position and the magnitude of reflection sites. With the addition of transverse scanning, this technique has been widely and successfully extended to the imaging of biological tissues, and is termed optical coherence tomography (OCT).
Optical Coherence Tomography (OCT) is a non-invasive, real-time imaging technique capable of obtaining images and making measurements on the order of about 10 microns or less. OCT has been used to measure the dimensions of the eye as described in U.S. Pat. Nos. 5,321,501 and 5,493,109.
The traditional interferometer configuration for OCDR or OCT is a standard Michelson interferometer. A light beam from a broadband source is input into a beam splitter, where the light beam is split and directed into a sample arm and a reference arm. An optical probe in the sample arm extends into a device that scans an object with a beam of light. The light beam input into the reference arm is reflected back by a reference mirror. The reflected reference beam from reference arm and the scattered sample beam from sample arm pass back through the beam splitter to a detector, which processes the signals by techniques known in the art to produce a backscatter profile or image on a display unit.
This configuration is limited to an optical efficiency of 25%, and 75% of the optical power supplied by the light source is wasted. If the light source cannot provide enough optical power, the interference light pattern may be too dim for the detector to detect.